This study is open to all eligible children diagnosed with newly diagnosed leukemia requiring two bone marrow aspirates or biopsies at least one week apart regardless of their race or sex. Additionally, patients must be > 4 yrs. of age and > 15 kg. due to the manufacturers recommendation for Fentanyl Oralet. There have been three patients enrolled to date. At present, enrollment has been temporarily halted due to unavailability of Fentanyl Oralet. A goal of ten patients in the first 4 months following delivery of new Oralets has been set.